Cannot send external emails - Urgent!

[aleonhardt]

Hi !

I've been troubleshooting this with MS together and we still seem to fail finding the actual problem.

Currently, only about 1K emails are being delivered to external addresses, if at all.

Other than that, anything that's more than i.e. 4k won't be delivered and is sitting in the queue waiting for its timeout

Anybody seen that before ?

Local mail delivery is absolutely fine. SMTP Service and IIS has been re-installed a few times, MS's SMTP Reinstall tool used as well to re-create Exchange connection, set all permissions to default, checked SMTP logfiles and all I can find is that the SMTP engine isn't ever sending QUIT to end the session, I guess this is because there are problems with the actual transfer of the data and it just "times out" after a while. All services, start up items, etc. are disabled, AV & AS disabled, still no change

Any help much appreciated !

Thanks !
ALex

 

[ilceres]

How strange....

I don't think that your SMTP service is setted for delivery only 4kb messages...

try to install a packet sniffer on Exch srv and listen your network!!... which tcp's connection goes e which not...

I use this

http://www.tamos.com/products/commview/

the trial is free
alternatively there are a lot of sniffers free
From network you can get your aswer

Italian are WORLD CHAMPION

 

[paulha]

Is this a new install ? If not, what changed prior to the problems ?

Can you ping the outside world from your server ?

 

[aleonhardt]

Hi,

Thanks for the sniffer !! have found out that the server is transferring data to the smtp, then suddenly nothing and the connectin times out

Anybody an idea what could cause this ?

Thanks !
Alex

 

[ilceres]

Ok...

If your local SMTP service attemp to connect the remote SMTP for deliver the mail but it can't and the connection time out should be a firewall problem...

check out if your firewall's rules permit the SMTP traffic to the WAN side - what kind of firewall you are behind?

if you used Comm View save the last connection log an send it to me.. maybe I can help you better




Italian are WORLD CHAMPION

 

[aleonhardt]

Hiya!

Well, it's a 3Com Firewall, basically a packet filter - and everything is allowed to go out, then again smtp is allowed to come in ..

I will limit outgoing traffic to only http, smtp.

Alex

 

[ilceres]

I can't undestand if you solved your problem.

However, you can't restrict only http and smtp. You have to let DNS traffic (port 53) to permit at your Exchange server the DNS resolution

Check it out... if your server can't solve domain name the connection will time out

Italian are WORLD CHAMPION

 

[aleonhardt]

Hi,

yeah - sorry, did add a few others as well so I can get remote access .. but still no change ;(

doing tests on the adsl connection which might shed some light as have figured that I cannot upload anything ! but I can download

Alex

 

[ilceres]

Did you check DNS resolution??

Italian are WORLD CHAMPION

 

[aleonhardt]

Hi !

I have news !!

The problem does not have anything to do with DNS, SMTP, SMTP Engine, Exchange, etc.

It looks like a DoS on that IP ! Or the ISP is messing with us ... Anyway, I chose a different IP (static ip) on the external interface of the Firewall after doing tons of tests & ran stats with ntop, etc. etc.

Guess what ?!? It's finally working !! All emails have been transfered ! Upload of files to ftp, etc. is working as well, ran ADSL speedtest - ran fine as well.

I got the ISP now to "investigate" what is happening on their network as Firewall, ADSL router and any internal possible virus/spyware/trojan are now excluded from being the actual problem.

Just in case you wonder, no the IP is not on any DNS blacklists I could find

Cheers for now .. will update once it's resolved.

Thanks for all the help!

Alex